Cavity-containing polyester film, resin composition, and production method for resin composition

Abstract

Provided is a cavity-containing polyester film that exhibits excellent lightness, film formability, concealing properties, and whiteness even in a case of mainly using a polyolefin resin (for example, polypropylene resin) as a cavity generating agent. The cavity-containing polyester film is a laminated body in which a first coating layer B1 that includes a polyester resin containing an inorganic pigment, a cavity-containing layer A that contains cavities inside, and a second coating layer B2 that includes a polyester resin containing an inorganic pigment are laminated in this order. This cavity-containing layer A includes a composition containing a polyester resin, a polyolefin resin, and a silicone resin. The apparent density of this cavity-containing polyester film is 0.80 g/cm 3 or more and 1.20 g/cm 3 or less. The inorganic pigment in the first coating layer B1 and second coating layer B2 is, for example, titanium oxide.

1 . A cavity-containing polyester film comprising:
 a first coating layer B1 that includes a polyester resin containing an inorganic pigment;   a cavity-containing layer A that contains cavities inside; and   a second coating layer B2 that includes a polyester resin containing an inorganic pigment,   wherein the first coating layer B1, the cavity-containing layer A, and the second coating layer B2 are laminated in this order,   the cavity-containing layer A includes a composition containing a polyester resin, a polyolefin resin, and a silicone resin, and   the cavity-containing polyester film has an apparent density of 0.80 g/cm 3  or more and 1.20 g/cm 3  or less.   
     
     
         2 . The cavity-containing polyester film according to  claim 1 , wherein a content of polydimethylsiloxane in the silicone resin in the cavity-containing layer A is 1 ppm or more and 2500 ppm or less with respect to a total mass of the cavity-containing layer A. 
     
     
         3 . The cavity-containing polyester film according to  claim 1 , wherein a content of polydimethylsiloxane in the silicone resin in the cavity-containing layer A is 0.005% by mass or more and 2.000% by mass or less with respect to 100% by mass of the polyolefin resin. 
     
     
         4 . The cavity-containing polyester film according to  claim 1 , wherein the inorganic pigment in the first coating layer B1 and second coating layer B2 is titanium oxide. 
     
     
         5 . The cavity-containing polyester film according to  claim 1 , wherein a ratio of a sum of a thickness of the first coating layer B1 and a thickness of the second coating layer B2 to a sum of the thickness of the first coating layer B1, a thickness of the cavity-containing layer A, and the thickness of the second coating layer B2 is 6% or more and 40% or less. 
     
     
         6 . The cavity-containing polyester film according to  claim 1 , which has a total light transmittance of 1% or more and 30% or less. 
     
     
         7 . The cavity-containing polyester film according to  claim 1 , which has an apparent density of 0.80 g/cm 3  or more and 1.10 g/cm 3  or less. 
     
     
         8 . The cavity-containing polyester film according to  claim 1 , which is used for a label, a card, a packaging material, or a release film. 
     
     
         9 . A resin composition comprising: an inorganic pigment; a polyester resin; a polyolefin resin; and a silicone resin, the resin composition being obtained by material recycling of the cavity-containing polyester film according to  claim 1 . 
     
     
         10 . A production method for a resin composition, comprising producing a resin composition containing an inorganic pigment, a polyester resin, a polyolefin resin, and a silicone resin by material recycling of the cavity-containing polyester film according to  claim 1 . 
     
     
         11 . The cavity-containing polyester film according to  claim 1 , wherein the polyester resin of the first coating layer B1 is polyethylene terephthalate,
 the polyester resin of the second coating layer B2 is polyethylene terephthalate, and   the polyester resin of the cavity-containing layer A is polyethylene terephthalate.   
     
     
         12 . The cavity-containing polyester film according to  claim 11 , wherein the polyethylene terephthalate of the first coating layer B1 is copolymerized with isophthalic acid,
 the polyethylene terephthalate of the second coating layer B2 is copolymerized with isophthalic acid, and   the polyethylene terephthalate of the cavity-containing layer A is copolymerized with isophthalic acid.   
     
     
         13 . The cavity-containing polyester film according to  claim 1 , wherein the polyolefin resin is polypropylene resin, polyethylene resin, or polymethylpentene resin. 
     
     
         14 . The cavity-containing polyester film according to  claim 1 , wherein the polyolefin resin is polypropylene resin. 
     
     
         15 . The cavity-containing polyester film according to  claim 14 , wherein the polypropylene resin has a propylene unit at 95 mol % or more. 
     
     
         16 . The cavity-containing polyester film according to  claim 14 , wherein the polypropylene resin is polypropylene homopolymer. 
     
     
         17 . The cavity-containing polyester film according to  claim 14 , wherein deflection temperature under load of the polypropylene resin is 85° C. or more. 
     
     
         18 . The cavity-containing polyester film according to  claim 1 , wherein the cavity-containing polyester film has a color tone b value of 4.0 or less. 
     
     
         19 . The cavity-containing polyester film according to  claim 1 , wherein thickness of the cavity-containing polyester film is 20 μm or more and 300 μm or less.